Neil Patrick Harris on Why His Relationship Is Work

Neil Patrick Harris says his relationship with David Burtka isn't just "happy family fantastic-ness." It's work.

They are on the cover of Out magazine's Love Issue and share the story of how they met, became a couple, and are now raising two kids.

"I initially fell for David harder than he fell for me," Harris tells Out. "I was in love with him before he was comfortable saying it, and I think that speaks to our past experiences. I remember saying, 'I think I love you,' and he was like, 'That's really nice,' which is not necessarily what you want to hear."

Harris says he's the quiet one, and Burtka is more like Tigger. They text each other constantly.

"I don't want to paint our relationship like we met and it's been happy family fantastic-ness ever since," he said. "What defines a relationship is the work that's involved to maintain it, and it's constantly changing. Sometimes I'm deeply in love with David and head-over-heels, and sometimes I question whether it's going to work out and is meant to be."

Burtka said their zodiac signs might have something to do with their fighting.

"Our fights last five minutes, then we're over it," Burtka said. "And we're both Gemini -- we have a good twin and a bad twin, and the four of us get along really well!"

Read their complete story and check out the intimate photos at Out.com.